1. Field of the Invention
The present invention relates to pipe lining techniques, and more particularly to a method of lining or repairing an aged or defective branch pipe which is conducted by using a pipe liner bag.
2. Description of the Related Art
When an underground pipe, such as pipelines and passageways, becomes defective or too old to perform properly, the pipe is repaired and rehabilitated without digging the earth to expose the pipe and disassembling the sections of the pipe. This non-digging method of repairing an underground pipe has been known and practiced commonly in the field of civil engineering. Typically, the method is disclosed by Japanese Provisional Patent Publication (Kokai) No. 60-242038.
According to the method described in the above-mentioned publication, the pipe repair method comprises inserting a sufficiently long tubular flexible liner bag into the pipe to be repaired by means of a pressurized fluid, like air and water. The tubular liner bag is made of a flexible resin-absorbent material impregnated with a thermosetting resin, and has the outer surface covered with an impermeable plastic film.
More particularly, according to the publication, the tubular flexible liner bag is closed at one end and open at the other; the tubular flexible liner bag is first flattened, then, the closed end of the tubular liner bag is tied to a control rope; the open end of the tubular liner bag is made to gape wide and hooked (anchored) at the end of the defective or old pipe in a manner such that the wide-opened end of the liner completely and fixedly covers and closes the pipe end; a portion of the liner is pushed into the pipe; then, the pressurized fluid is applied to the portion of the tubular liner such that the fluid urges the tubular liner to enter the pipe. Since one end of the tubular liner is hooked at the end of the pipe, it remains there while the rest of the flexible liner bag is turned inside out as it proceeds deeper in the pipe. (Hereinafter, this manner of procedure shall be called "everting".) When the entire length of the tubular liner bag is everted (i.e., turned inside out) into the pipe, the control rope holds the closed end of the tubular liner bag to thereby control the length of the tubular liner in the pipe. Then, the everted tubular liner is pressed against the inner wall of the pipe by the pressurized fluid, and the tubular flexible liner is hardened as the thermosetting resin impregnated in the liner is heated, which is effected by heating the fluid filling the tubular liner bag by means of a hot steam, etc. It is thus possible to line the inside wall of the defective or old pipe with a rigid liner without digging the ground and disassembling the pipe sections.
The above-mentioned method may also be applied to the lining of a branch pipe which is branched from a main pipe, an example of which is illustrated in FIG. 6.
FIG. 6 is a cross-sectional view showing a conventional method of lining a branch pipe. A pressure bag 116 for everting a branch pipe liner bag 104 is inserted into a main pipe 101. A branch pipe 102 to be repaired is branched from the main pipe 101 as illustrated. Since this pressure bag 116 must be separated from the branch pipe liner bag 104, a sealing tube 140 should be connected to the pressure bag 116 in order to apply a pressure to the branch pipe liner bag 104.
Then, the pressure bag 116 is supplied with compressed air to evert both the sealing tube 140 and the branch pipe liner bag 104 into the branch pipe 102. While the illustrated state is being maintained, the branch pipe liner bag 104 is, for example, heated to harden a hardenable resin impregnated therein. Thereafter, when the sealing tube 140 is pulled out from the branch pipe 102 (branch pipe liner bag 104), the branch pipe 102 is reinforced by the hardened branch pipe liner bag 104 which has been lined on the inner wall of the branch pipe 102.
The above-mentioned method, however, must prepare the sealing tube 140 of an appropriate size in accordance with the length of the branch pipe 102 to be repaired each time the lining is performed. Therefore, the sealing tube 140 must be exchanged for each branch pipe according to its length.
To solve this problem, a branch pipe lining method as shown in FIGS. 7-9 has been proposed.
More specifically, FIGS. 7-9 are cross-sectional views showing a conventional branch pipe lining method in the order of processes included therein. As shown in FIG. 7, this method utilizes a fluid pressure sealing nozzle 207 to provide an airtight connection between a pressure bag 216 and a branch pipe liner bag 204. More specifically, the fluid pressure sealing nozzle 207 is air-tight connected with a flange 204A formed on one end of the branch pipe liner bag 204 by one of sealing structures shown in FIGS. 10(a)-10(d).
These sealing structures will be explained below in detail with reference to FIGS. 10(a)-10(d).
In a sealing structure shown in FIG. 10(a), a fluid pressure sealing nozzle 207 is formed with a tapered protrusion 207a which is used to maintain an air-tight connection between the fluid pressure sealing nozzle 207 and the branch pipe liner bag 204.
A sealing structure shown in FIG. 10(b) maintains an air-tight connection between the fluid pressure sealing nozzle 207 and the branch pipe liner bag 204 by means of an O-ring 230 provided in the fluid pressure sealing nozzle 207. Another sealing structure shown in FIG. 10(c) utilizes a valve 231 provided on the fluid pressure sealing nozzle 207 for realizing a similar air-tight connection.
FIG. 10(d) shows a sealing structure for maintaining an air-tight connection between the fluid pressure sealing nozzle 207 and the branch pipe liner bag 204 by means of a magnetic plate 232 embedded in the flange 204A of the branch pipe liner bag 204 and a magnet 233 arranged on the nozzle 207 at a location opposing to the magnetic plate 232 such that the magnetic plate 232 and the magnet 233 attract to each other.
Now, referring back to FIG. 7, the flange 204A of the branch pipe liner bag 204, after accommodated in the pressure bag 216, is placed on the fluid pressure sealing nozzle 207. A working robot 203 is driven to press the flange 204A of the branch pipe liner bag 204 onto the inner wall of the main pipe 201 to provide a close contact therebetween. A compressor 209 is next driven to supply compressed air into the pressure bag 216 through an air hose 18 to cause the branch pipe liner bag 204 to evert by the action of the pressure of the compressed air and enter into the branch pipe 202 from the main pipe 201 toward the ground (in the upward direction). When the insertion of the branch pipe liner bag 204 has been completed over the whole length of the branch pipe 202, a pressure cap 250 is attached to the upper end of the branch pipe liner bag 204, as shown in FIG. 8. Through a hot water hose 221 and an air hose 222 connected to the cap 250, hot water and compressed air are respectively supplied into the branch pipe liner bag 204.
The branch pipe liner bag 204 is inflated by the pressure of the compressed air to be pressed against the inner wall of the branch pipe 202 as illustrated. Simultaneously, the supplied hot water provides the branch pipe liner bag 204 with heat so that a thermosetting resin impregnated in the liner bag 204 is hardened by the heat.
In this manner, the branch pipe liner bag 204 is hardened while it remains pressed against the inner wall of the branch pipe 202, whereby the inner wall surface of the branch pipe 202 is lined or repaired by the hardened branch pipe liner bag 204.
After the branch pipe liner bag 204 has been hardened, the working robot 203 is driven to lower the fluid pressure sealing nozzle 207 to release the fluid pressure sealing nozzle 207 from the flange 204A of the branch pipe liner bag 204.
Then, a pull rope 208 is pulled in the direction indicated by the arrow in FIG. 9 to move the working robot 203 in the same direction along the main pipe 101. This causes the fluid pressure sealing nozzle 207 and the pressure bag 216 to also move in the same direction for removal from the main pipe 101. Consequently, the hardened branch pipe liner bag 204 only remains on the inner wall of the branch pipe 202, thus completing a sequence of lining operations for the branch pipe 202.
As described above, this method does not need the sealing tube 140 as the method shown in FIG. 6 and accordingly removes the replacing operation of the sealing tube 140.
However, the sealing structures shown in FIGS. 10(a)-10(d) between the branch pipe liner bag 204 and the fluid pressure sealing nozzle 207, employed in the conventional branch pipe lining method described above, may sometimes have difficulties in constantly ensuring a sufficiently high sealability.
In addition to the problem mentioned above, the conventional method further implies an economical problem. Specifically explaining with reference FIG. 8, since the diameter of a space for access to generally used branch pipes is approximately .phi.400 m/m, which is smaller than the diameter of main pipes being approximately .phi.900 m/m, operations within the access space to the branch pipe is impossible or quite difficult to be performed. It is therefore necessary to employ a branch pipe liner bag long enough to reach the ground through the branch pipe such that associated operations may be done on the ground. For this reason, a branch pipe liner bag 204, long enough, is employed such that a pressure cap 250 is attached to the upper end thereof on the ground after it is everted and passed through the branch pipe to be repaired. Since this pressure cap 250 is provided with a hot water hose 221 and an air hose 222 mounted thereon, operations are troublesome. Moreover, this method requires a branch pipe liner bag which is longer than a branch pipe to be repaired by a length extending from the end of the branch pipe to the ground or a location where the associated operations are performed, which is not preferable in view of the economy.